The document discusses different locations where gas can accumulate in the abdomen and pelvis, including intraperitoneal, retroperitoneal, bowel wall, gallbladder, and abscess. It provides examples of various imaging findings that can indicate the presence of gas in these different locations and potential etiologies for how the gas may have accumulated in each space.

1. Abnormal Gas..Basic
concepts
Dr/Ahmed Bahnassy
Consultant Radiologist
MBCHB-MD-FRCR
E-mail:aatteya2001@yahoo.com

2. Where is the gas ?
 IP
 RP
 BW  Intraperitoneal
 GB  Retroperitoneal
 AB  Bowel wall
 Gall bladder and
biliary
 Abscess

3. PNEUMOPERITONEUM

4. FREE AIR
SENSITIVITY OF IMAGING STUDIES
 COMPUTED TOMOGRAPHY 99%
 LATERAL UPRIGHT CHEST RADIOGRAPH 98%
 AP UPRIGHT CHEST RADIOGRAPH 80 - 90%
 SUPINE ABDOMEN RADIOGRAPH ?

5. PNEUMOPERITONEUM
SENSITIVITY OF IMAGING STUDIES
 RADIOLOGIC DEMONSTRATION DEPENDS ON:
– VOLUME OF FREE AIR
– TIME INTERVAL BEFORE IMAGING
– TYPE OF IMAGING
– CONDUCT OF IMAGING EXAMINATION
 AS LITTLE AS ONE CC CAN BE DEMONSTRATED
 10% OF PATIENTS WITH PERFORATED ULCERS
DO NOT DEMONSTRATE PNEUMOPERITONEUM

6. UPRIGHT CHEST

7. PNEUMOPERITONEUM
UPRIGHT RADIOGRAPHS
UPRIGHT ABD CENTRAL TENDON
UNDER RIGHT HEMIDIAPHRAGM AND HEMIDIAPHRAGM

8. FREE AIR…….DECUBITUS VIEW
GAS BETWEEN LIVER AND BODY WALL
BUT MAY ALSO BE IN OR ONLY IN THE PELVIS

9. FREE AIR
CENTRAL TENDON

10. FREE AIR
CENTRAL TENDON

11. RIGLER’S SIGN
BOTH SIDES OF BOWEL WALL VISIBLE
DOUBLE WALL SIGN

12. MASSIVE PNEUMOPERITONEUM
FOOTBALL SIGN

13. FALCIFORM LIGAMENT
GAS BUBBLE OVER LIVER

14. FALCIFORM LIGAMENT

15. PNEUMOPERITONEUM
SUBHEPATIC GAS BUBBLE

16. DIVERTICULITIS
PNEUMOPERITONEUM

17. ANTERIOR ABDOMINAL WALL
ANATOMIC FOLDS

18. FREE AIR
INFERIOR EPIGASTRIC VESSELS
(LATERAL UMBILICAL LIGAMENTS)

19. PSEUDO-
PNEUMOPERITONEUM

20. CENTRAL TENDON GAS
YES, BUT JUST THE STOMACH

21. GAS UNDER THE RIGHT HEMIDIAPHRAGM
HEPATIC FLEXURE ANTERIOR-SUPERIOR TO LIVER

22. SUBDIAPHRAGMATIC FAT
SIMULATING FREE AIR

23. FREE AIR OR NOT FREE AIR?
THAT IS THE QUESTION
PNEUMOTHORAX SIMULATES FREE AIR

24. RETROPERITONEAL GAS
SIMULATES FREE AIR

25. RETROPERITONEAL GAS

26. RETROPERITONEAL GAS
CAUSES
 IATROGENIC
– SURGERY
– DIAGNOSTIC PROCEDURE
 TRAUMA
– PENETRATING
– RUPTURED VISCUS
 RETROPERITONEAL DUODENUM, COLON, RECTUM
 PERFORATED BOWEL
 SECONDARY TO TUMOR, INFECTION, OBSTRUCTION,
NECROSIS
 CAUDAL EXTENSION OF PNEUMOMEDIASTINUM
 GAS WITHIN ABSCESS

27. RETROPERITONEAL GAS
IMAGING
 LITTLE CHANGE IN POSITION OR SHAPE WHEN
COMPARING SUPINE, UPRIGHT, DECUB
RADIOGRAPHS
 BUT FREE INTRAPERITONEAL GAS IS FREELY MOBILE
 TENDS TO STAY IN ONE RETROPERITONEAL
COMPARTMENT
 DUODENAL PERFORATION…..RUQ ANTERIOR PARARENAL
SPACE
 SIGMOID DIVERTICULITIS….. LLQ
 PERIRENAL ABSCESS…………. PERINEPHRIC SPACE
 OFTEN FORMS LINEAR, CURVILINEAR GAS
COLLECTIONS

28. Severe dysuria-left flank pain

29. RETROPERITONEAL GAS
IMAGING
 BENEATH DIAPHRAGM CAN SIMULATE
PNEUMOTHORAX
 LARGE VOLUME OF GAS CAN OUTLINE
RETROPERITONEAL STRUCTURES
 KIDNEY, LIVER MARGIN, PSOAS, FLANK STRIPE
 RETROPERITONEAL GAS CAN EXTEND
 CEPHALAD TO MEDIASTINUM
 FASCIAL PLANES OF BODY WALL AND EXTREMITIES
 INTO PERITONEAL CAVITY

30. RETROPERITONEAL GAS

31. 13-YEAR-OLD GIRL WITH CROHN’S DISEASE
HAS SUBACUTE FEVER AND ABD PAIN

32. RETROPERITONEAL GAS
EXTENDS TO POSTERIOR PARARENAL SPACE & THEN PROPERITONEAL FAT

33. AFTER COLONOSCOPY AND
BIOPSY
EXTENSIVE RETROPERITONEAL GAS

34. BAROTRAUMA
MEDIASTINUM – RETROPERITONEUM – FREE AIR

35. BOWEL WALL GAS

36. PNEUMATOSIS OF COLON
INFANT ADULT
NECROTIZING ENTEROCOLITIS
ISCHEMIC COLITIS

37. WHAT IS THE ABNORMALITY
HERE?
USE LUNG WINDOWS TO LOOK FOR GAS

38. 72-YEAR-OLD WOMAN WITH DIARREHA

39. 58-YEAR-OLD WOMAN
MILD ABDOMINAL PAIN FOR 2 DAYS
SCLERODERMA,
GAS IN COLON WALL

40. PNEUMATOSIS 2 DAYS AFTER SEGMENTAL SB RESECTION
RESOLVED SPONTANEOUSLY

41. ASYMPTOMATIC 40-YEAR-OLD MAN
BENIGN STEADY STATE PNEUMATOSIS

42. ISCHEMIC BOWEL

43. ISCHEMIC BOWEL
IMAGING SIGNS
– DILATION
 PSEUDOOBSTRUCTION
– BOWEL WALL
 THICKENED
 PNEUMATOSIS
 UNENHANCING
– GAS IN VESSELS
 MESENTERIC, SMV, PORTAL VEINS
– OBSTRUCTED VESSELS
 SMA, SMV
– HIGH DENSITY CLOT ON UNENHANCED CT
– FILLING DEFECTS ON CT WITH IV CONTRAST
– ASCITES, FREE AIR AFTER PERFORATION

44. ACUTE ONSET OF ABDOMINAL PAIN
SMA EMBOLIS

45. Thumprinting

46. SBO
ISCHEMIC BOWEL
AT SURGERY: SB TWISTED UNDER
ADHESION

47. ISCHEMIC SMALL BOWEL
ETIOLOGY ?
SMV CLOT

48. Gall bladder and Biliary GAS

49. BILE DUCT GAS
 IATROGENIC
– BILE DUCT SURGERY
– SPHINCTEROTOMY
 BILIARY FISTULA
– GALLSTONE ERODING INTO BOWEL
– DUODENAL ULCER
– UPPER ABDOMINAL MALIGNANCY
– TRAUMA
 CHOLANGITIS
– GAS FORMING ORGANISM

50. BILE DUCT GAS
BILE DUCT GAS
CHUNKY AND CENTRAL

51. BILE DUCT GAS AND SBO

52. SBO GALLSTONE ILEUS

53. GALLSTONE ILEUS

54. GALLSTONE ILEUS
BILE DUCT GAS, SBO, STONE

55. GALLBLADDER GAS
 GALLBLADDER LUMEN
– GALLBLADDER-BOWEL FISTULA
– GALLSTONE ILEUS
– EMPHYSEMATOUS CHOLECYSTITIS
 GALLBLADDER WALL GAS
– EMPHYSEMATOUS CHOLECYSTITIS

56. EMPHYSEMATOUS CHOLECYSTITIS

57. PORTAL VEIN GAS

58. SMALL BOWEL ISCHEMIA
GAS IN MESENTERIC AND PORTAL VEINS
48 SubPhrenic Abs CT

59. 65-YEAR-OLD MAN
ABDOMINAL PAIN
PORTAL VEIN GAS
DELICATE AND PERIPHERAL

60. 36-YEAR-OLD MAN
MULTIPLE CONGENITAL ANOMALIES
FEVER , WBC 17.8, 15 BANDS
ISCHEMIA OF SB AND STOMACH

61. ABSCESS

62. ABSCESS
 SUSPECT AN ABSCESS WHEN RADIOGRAPHS
SHOW A GAS COLLECTION THAT IS ABNORMAL
BECAUSE OF PERSISTENCE ON MULTIPLE
VIEWS
 GET HISTORY, PX, LAB DATA BY
CONSULTATION WITH ORDERING MD.
 CONFIRM WITH CROSS-SECTIONAL IMAGING

63. APPENDICEAL ABSCESS
RETROCECAL APPENDIX
ABNORMAL GAS… UNCHANGED ON MULTIPLE VIEWS

64. SIGMOID DIVERTICULITIS
GAS FILLED “DIVERTICULUM!!

65. Huge Abscess !

66. FEVER 10 DAYS AFTER
ABDOMINAL SURGERY

67. CROHN’S DISEASE WITH ABSCESS

68. PANCREATIC ABSCESS

69. PANCREATIC GAS
-only 3 causes
 GAS IN PANCREATIC BED
– ABSCESS
– POST PANCREATIC DRAINAGE
PROCEDURE
 PERCUTANEOUS OR SURGICAL
– PUESTOW PROCEDURE
– PSEUDOCYST
– PANCREATIC FISTULA

70. PANCREATITIS WITH ABSCESS
LESSER SAC ABSCESS
GAS IN PANCREATIC ABSCESS

71. PANCREAS-GAS BUT NO ABSCESS
PANCREAS-COLON FISTULA

72. LESSER SAC

73. GAS IN LESSER SAC
PERFORATED GASTRIC ULCER

74. GASTRIC ULCER
PERFORATION INTO LESSER SAC

75. Pancreatic Abscess.

76. Summary
IP
RP
BW
GB
AB